1. Field of the Invention
This invention lies in the field of surface etching methods using laser radiation for dielectric oxide ceramics and dielectric single crystal oxides.
2. Prior Art
It is known that materials can be worked with laser radiation. Such working can involve etching, cutting or drilling. As a rule, the function of the laser radiation upon the material being worked is to remove a portion of such material in a manner comparable to an etching operation wherein the removed material is highly heated and burns at least in part in a surrounding oxygen atmosphere.
U.S. Pat. No. 3,601,576 discloses drilling of certain crystals with pulsed laser radiation for clocks. This laser beam processing ensues in an oxidizing, a reducing, or in a neutral atmosphere. An oxidizing atmosphere is preferred. Under the conditions provided the crystal can be heated before being subjected to the laser beam working.
IBM Technical Disclosure Bulletin, Vol. 25, No. 7a (December 1982), page 3256, discloses the etching of ferrite material with laser radiation in a halomethane gas atmosphere. Carbon tetrachloride, carbon tetrafluoride and sulfur hexafluoride are also employed instead of the halomethane gas. Obviously, the halogen content in the atmosphere is critical for the known working of the ferrite material with laser radiation.
Applied Physics Letters, Vol. 40 (1982), pages 352-354, discloses the working of some ceramic materials with laser radiation in addition to silicon. The chosen starting material is submersed in an aqueous potassium hydroxide solution for intensifying the etching effect. An aluminum oxide/titanium carbide ceramic is specified as specific material. Just as in the method of the publication cited above, a liquid, or, alternatively, a gas which has aggressive property with respect to circuit structures and the like and which is already present on the material to be processed is allowed to influence such material during the processing. For example, a fine interconnect structure already present on the material to be processed is negatively influenced by a halogen atmosphere or a caustic solution.
Elektronik Produktion und Pruftechnik (May 1982), pages 347-353, specifies various processing methods, suitable for example, for ceramic substrates among others, wherein laser radiation is employed. A compressed air stream and/or an extraction are provided therein, principally in order to protect the optical parts of the apparatus against particles which are hurled off when the substrate material is scored, cut, drilled.
The published European Patent application No. 00 13 345 discloses the employment of argon ion lasers for processing operations in semiconductor technology.
The German OS No. 19 01 524 discloses the processing of semiconductor material, particularly silicon, by laser beam heating, principally in an atmosphere which contains a volatile compound. The atmosphere provided for this purpose serves the purpose of oxidizing the silicon to form, for example, hydrosilicon (SiH.sub.4). Hydrogen is present as a carrier gas for achieving good thermal conduction without the oxidation of the silicon provided in this method being noticibly impeded due to this gas. The hydrogen becomes an inert gas therein and is equated with the employment of nitrogen or other inert gas.
Internal experiments have been undertaken with the aim of providing a method of etching with laser radiation a material such as a dielectric oxide ceramic, or, alternatively, dielectric oxide crystals, particularly single-crystals, whereby a perovskite material especially is involved. It is thus a matter, for example, of using barium titanate, strontium titanate, lead zirconate titanate, and the like, that is, principally dielectric materials which have wide-spread application in electronics, particularly for piezo-electric bodies as well. The results of the numerous experiments carried out were completely unsatisfactory and these results likewise did not allow any conclusions that such an etching could lead to a satisfactory result at all for bodies of such a material.